1996 Chevrolet Caprice - drive train is making noise

Question

When I speed up in my 1996 caprice I hear pinging sounds that sound like little rocks hitting my drive shaft. would that be u joints? it only does it at lower speeds.

Answer 1

You will need to inspect your driveshaft for security from front to rear, bolts, joints, brackets and for any damage. Are you sure the pinging is from your driveshaft? Pinging is normally associated with engine pinking, especially when accelerating from a low speed.

Answer 2

This sounds like one (or both) of your u-joints is (are) bad. If the u-joint has dried out and the needle bearings are dry, when they rotate as they are supposed to, they bind/release causing a pinging noise like you are describing (it reverberates through the hollow drive shaft). The reason you only hear it at lower speeds is because the road noise covers it at some point. Believe me when I say, it's still happening.

It is pretty easy to see if this is the problem by taking your drive line down and manipulating the u-joint. If it is bad, it will either not want to move, or it will have a lot of crunchy feeling to it as you rock it back and forth.

When changing or inspecting a u-joint, it is important that you get the the drive shaft and differential yoke back in the same position you took it apart as ... This is easily accomplished by using a permanent marker, like a Sharpie, and marking a straight line from the yoke to the drive shaft. If you don't, an out of balance situation can occur. It doesn't happen all the time, but it can. Marking it and putting it back in the same position will save you having to move it 180 degrees after you've already installed it once.

Also, if you replace your u-joint with one which has a grease-zerk, ensure you put the zerk on the compression side between the drive line yoke and the differential yoke. This is imperative as well, because if you don't, the u-joint will fail prematurely at the zerk. The zerk sits inside of a hole. When the zerk is on the compression side, stress is transmitted through the zerk from one side of the zerk hole to the other. When on the tension side, there forms a stress riser with nothing to support the zerk hole, so a crack can form and ultimate failure will occur.

To discover what the compression side is, look at this picture:

First of all, the zerk is the red thing protruding between cap 1 and 2 of the u-joint. The arrows denote the direction of the drive shaft as if you were looking down its length from the front of the car towards the rear differential. This next part might be confusing, so this is from the stand point of the rear u-joint. If the loops of your drive shaft yoke are on caps 1 & 3, while the yoke of the differential is on 2 & 4, then the zerk would be in the correct position to be on the compression side. There is another compression area between 3 & 4. There is a tension area between 1 & 4, as well as 2 & 3. If you are doing the u-joint at the front of the drive shaft, then the transmission yoke would be at the 1 & 3 position and drive shaft at the 2 & 4.